Conventionally, packaging materials such as food containers have been required to be provided with water and oil repellency. As a method for imparting water and oil repellency to a surface of an object, for example, there is known a method by which a surface of an object is provided with irregularities using particulates of metal oxide or the like d further coated with a water- and oil-repellent material like a fluoropolymer.
For example, Patent Document 1 discloses a method in which metal oxide particulates coated with a specific fluororesin are used; Patent Document 2 discloses a method in which a composition composed of a binder such as a silicone resin, particulates of silica or the like, and a water- and oil-repellent compound such as a fluorine-containing compound is used; Patent Document 3 discloses a method in which a dispersion of a silica having a specific particle diameter in a fluororesin is used; and Patent Document 4 discloses a method in which a composition composed of an aggregate and a fluororesin or the like is used.
On the other hand, methods are known in which when a surface of an article made of, for example, paper or fiber is coated with a water- and oil-repellent material such as a fluoropolymer, a water-soluble polymer such as polyvinyl alcohol, polyacrylamide, and starch is used in combination therewith, in order to strengthen the coating (see, for example, Patent Documents 5 to 7).